As shown in JP-U-4-105906A, the valve controller changes valve timing of an intake valve and/or an exhaust valve by rotational torque of an electric motor. Alternatively, the valve controller changes valve lift of an intake valve and/or an exhaust valve by rotational torque of an electric motor as shown in JP-11-324625A.
In such a valve controller, an electric current supplied from a driving circuit to the motor is controlled by a control circuit. A control signal is generated in the control circuit according to a rotation number signal detected by a rotation sensor which detects an actual rotation number of the motor. A rotational position signal of the motor is detected by a rotational position sensor. The operation of the motor is controlled based on the control signal and the rotational position signal.
The conventional valve controller driven by the electric motor needs the rotation number sensor and the rotational position sensor independently. Thus, the size of the valve controller becomes large and the production cost increases.